Video Connectors Tutorial

Radio Frequency (RF)

RF is the oldest way to transmit video signals. It is used on older TVs, VCRs, cable TV receptors, and video game consoles (think of the Atari 2600 and the Nintendo Entertainment System) where you have to tune the TV to channels 3 or 4 to get the image being generated by these devices. This kind of connection can be used to connect your VCR or cable TV box to your TV, but since nowadays all TVs have better video connections, you should use one of them in order to get a better image quality. In summary, use the RF connection only if you are hooking up a 1980’s video game console to your TV; otherwise, use one of the video connections described in the following pages.

There are two types of RF cables: 75-ohm coaxial and 300-ohm parallel. This second type was used by old terrestrial broadcasting antennas, but even this kind of antenna uses the 75-ohm coaxial cable presently. You can install a 300-ohm cable/connector into a 75-ohm connector by using an adapter, as we show in Figure 6.

In Figure 1, you can see the RF input on a TV set. On this plug, you should connect your old cable TV receptor, a 1980’s video game console, or your antenna, if you still use analog terrestrial TV. (Currently, in the U.S., terrestrial broadcasting is done only in digital format, so you will need an adaptor box similar to a cable TV box to be able to watch terrestrial broadcasting if you have an analog TV. If your TV is still based on a cathode ray tube, i.e., it is not a flat-screen TV, it is analog.) If the device you want to hook up to the TV has a better type of connection, you should use it instead if both your TV set and the device support a better kind of connection.

RF connectorFigure 1: RF input on a TV set

In Figure 2, you can see RF input and output on a VCR. The input is used to connect the VCR to older cable TV boxes or a TV antenna. The output can be used to connect the VCR to the TV, but this connection shouldn’t be done nowadays, since you can use composite video to connect your VCR to your TV, which provides a better image quality.

RF connectorFigure 2: RF input and output on a VCR

On computers, RF connectors are only used on TV cards or video capture cards to allow you to watch and record live TV shows on your computer, connecting the RF input plug to a cable TV box or a TV antenna. If you have a video capture card, don’t use this connector to hook a VCR to your PC, since you can use the composite video connection, which is better.

RF connectorFigure 3: RF inputs for TV antenna and FM antenna on a video capture board

In Figure 4, you can see a typical RF cable and connector, and in Figure 5 another kind of connector that also can be used on RF connections. The difference between them is that the cable connector in Figure 4 is meant to be screwed to the female connector on your TV, VCR or cable TV box, while the second connector, in Figure 5, doesn’t need to be screwed, just push it towards the female connector and it will fit.

RF cableFigure 4: Typical RF male connector and cable (screw type)

RF cableFigure 5: Another kind of RF male connector

RF conversorFigure 6: Adaptor to convert 300-ohm RF input (“old type”) into a 75-ohm plug (“balun”)

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Author: Gabriel Torres

Gabriel Torres is a Brazilian best-selling ICT expert, with 24 books published. He started his online career in 1996, when he launched Clube do Hardware, which is one of the oldest and largest websites about technology in Brazil. He created Hardware Secrets in 1999 to expand his knowledge outside his home country.

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